The present invention relates to drift compensation of measuring instruments, and more particularly the invention relates to drift compensation in the circuit that processes the signals provided by an analyzer, such as a gas analyzer.
The German printed patent application 1,965,804 describes a gas analyzer with measuring signal amplifier wherein a program device causes reference gases to be provided to the gas analyzer for establishing therein particular measuring states resulting in particular output signals of the amplifier, which are then varied to agree with reference signals for these specific measuring states. The variation involves variation of resistance devices. This kind of adjustment as carried out by the known apparatus yields correct drift compensation only if one of the reference gases is such that the analyzer output is to represent an exact zero condition of whatever component it is looking for normally. This, however, is a considerable constraint. If, for any reason, such zero point adjustment is not possible, then the result of the adjustment in one instance is, in fact, altered by the subsequent adjustment for the other reference gas. The correction, therefore, must be repeated, possibly several times, and the equipment alternates back and forth between the two reference gases and measuring states to obtain a stepwise approximation process of adjustment.